Devices for expressing human breast milk are well known. In principle, there are two different types: the first device type is operated manually, i.e. the negative pressure required for the expressing operation is generated by manual actuation of the vacuum pump. In the devices of the second type, the vacuum pump is operated electrically, it being possible for the vacuum pump to be connected to the power supply network and/or to be operated via a battery or another energy accumulator. Examples for this include WO 96/22116, US 2009/0099511, US 2008/0287037, U.S. Pat. No. 7,094,217 and US 2008/0039781.
The vacuum pumps are connected to a breast shield either directly or via vacuum lines. The breast shield usually has a funnel-shaped part for receiving part of the mother's breast including the nipple. As a rule, the funnel-shaped part merges into a part, which is in the shape of a hollow cylinder and to which, firstly, either the vacuum pump is connected directly or via a suction line and which, secondly, is likewise connected directly or via a milk line to a milk collecting container. It is known to select breast shields in accordance with the size of the breast. In particular, breast shield sets are known, in which the size of the funnel-shaped part can be selected according to the mother.
Relatively small breast shields are also known in the prior art. U.S. Pat. No. 6,379,327 discloses a portable, so called “hands-free” expressing device. In this context, “hands-free” means that, once switched on, the entire expressing device functions without hands, i.e. that neither the pump nor the breast shield have to be held by hand. In US'327, a small funnel-shaped breast shield is fastened for this purpose to the breast using straps. A first tube leads from the breast shield to a vacuum pump, which is held in a belt. A second tube leads from the breast shield into a milk collecting container, which can be carried in the same belt.
WO 02/102437 and WO 2008/137678 show “hands-free” expressing devices as well. Here, the breast shield is in each case integrated into a pump housing and serves at the same time as a diaphragm for generating a negative pressure.
U.S. Pat. No. 949,414 describes a funnel-shaped breast shield, which can be arranged under a bra. Rather than a vacuum being applied, a tube leads from the breast shield to a baby who is intended to obtain the milk desired by sucking on the tube.
U.S. Pat. No. 6,440,100 shows a device for expressing breast milk with a small breast shield, which can be worn under the bra. A milk tube leads from the breast shield to a milk collecting container. The container is connected via a vacuum tube to a vacuum source. The milk collecting container is evacuated by means of the vacuum source, with the negative pressure being applied to the breast shield via the milk tube. Because of the negative pressure prevailing in the milk collecting container, expressed milk is to pass into the milk collecting container via the milk tube. As an alternative, the milk collecting container itself can serve as a vacuum pump. The device has the disadvantage that the relatively large volume of the milk collecting container likewise has to be evacuated. The “dead volume” considerably restricts the performance of the device.